Maintaining sequentiality for media management of a memory sub-system

ABSTRACT

Methods, systems, and devices for maintaining sequentiality for media management of a memory sub-system are described. A plurality of read commands in connection with a set of media management operations for a plurality of transfer units are issued according to a read sequence. A plurality of entries associated with the set of media management operations are stored. A plurality of write commands in connection with the set of media management operations are issued based on the plurality of entries of the read sequence.

TECHNICAL FIELD

The following relates generally to a memory sub-system and more specifically to maintaining sequentiality for media management of a memory sub-system.

BACKGROUND

A memory sub-system can include one or more memory components that store data. The memory components can be, for example, non-volatile memory components and volatile memory components. In general, a host system can utilize a memory sub-system to store data at the memory components and to retrieve data from the memory components.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the disclosure. The drawings, however, should not be taken to limit the disclosure to the specific embodiments, but are for explanation and understanding only.

FIG. 1 illustrates an example computing system that includes a memory sub-system in accordance with some examples of the present disclosure.

FIG. 2 is a flow diagram of an example method for maintaining sequentiality for media management of a memory sub-system in accordance with some examples of the present disclosure.

FIG. 3 is a block diagram of an example method for maintaining sequentiality for media management of a memory sub-system in accordance with some examples of the present disclosure.

FIG. 4 is an example of a scoreboard maintaining sequentiality for media management of a memory sub-system in accordance with some examples of the present disclosure.

FIG. 5 is a block diagram of an example computer system in which examples of the present disclosure can operate.

DETAILED DESCRIPTION

Aspects of the present disclosure are directed to maintaining operation and/or data sequentiality for media management for a memory sub-system. A memory sub-system can be a storage device, a memory module, or a hybrid of a storage device and memory module. Examples of storage devices and memory modules are described with reference to FIG. 1. In general, a host system can utilize a memory sub-system that includes one or more memory devices that store data. The host system can provide data to be stored at the memory sub-system and can request data to be retrieved from the memory sub-system.

A memory device can be a non-volatile memory device. A non-volatile memory device is a package of one or more dice. Each die can consist of one or more planes. For some types of non-volatile memory devices (e.g., negative-and (NAND) devices), each plane consists of a set of physical blocks. Each block consists of a set of pages. Each page consists of a set of memory cells, which store bits of data. For some memory devices, such as NAND devices, blocks are the smallest area than can be erased and pages within the blocks cannot be erased individually. For such devices, erase operations are performed one block at a time.

A page of a block can contain valid data, invalid data, or no data. Invalid data is data that is marked as outdated as a new version of the data is stored on the memory device. Invalid data includes data that was previously written but is no longer associated with a valid logical address, such as a logical address referenced by a host system in a physical to logical (P2L) mapping table. Valid data is the most recent version of such data being stored on the memory device. A memory sub-system can mark data as invalid based on information received, for example, from an operating system. A page that does not contain data includes a page that has been previously erased, and not yet written to.

A memory sub-system controller can perform operations for media management algorithms, such as wear leveling, refresh, garbage collection, scrub, etc. A block may have some pages containing valid data and some pages containing invalid data. To avoid waiting for all of the pages in the block to have invalid data in order to erase and reuse the block, an algorithm hereinafter referred to as “garbage collection” can be invoked to allow the block to be erased and released as a free block for subsequent write operations. Garbage collection is a set of media management operations that include, for example, selecting a block that contains valid and invalid data, selecting pages in the block that contain valid data, copying the valid data to new locations (e.g., free pages in another block), marking the data in the previously selected pages as invalid, and erasing the selected block.

“Garbage collection” hereinafter refers to selecting a block, rewriting the valid data from the selected block to another block, and erasing all invalid data and valid data stored at the selected block. The valid data from multiple selected blocks can be copied to a smaller number of other blocks and the selected blocks can then be erased. As a result, the number of blocks that have been erased can be increased such that more blocks are available to store subsequent data from a host system.

During garbage collection, valid data of the block to be erased is initially read into and stored by a buffer based on one or more read commands issued by a memory sub-system controller and the corresponding page (e.g., the page on which the valid data is contained) is erased. The valid data can then be written (e.g., re-written) to the memory device (e.g., to a different page of the memory device). In order to write the valid data to a location (e.g., a different page of the memory device), write commands are issued by the memory sub-system controller, each write command indicating a memory address (e.g., a destination memory address) to which the valid data is to be written.

In some garbage collection procedures, the write commands are issued once the corresponding read command has been completed. The read commands are issued in a given order (e.g., a first, sequential order), but traditionally in some cases, the read commands are not completed in the same order. As write commands are issued once a corresponding read command is complete, the write commands are not issued in the same order in which the read commands were issued (i.e., the write commands are issued in a non-sequential manner with respect to the order of the issued read commands). Such conventional writing techniques (e.g., writing valid data back to a block in a non-sequential manner during a garbage collection procedure) can result in the memory sub-system experiencing a performance loss as blocks of data are written to pages out of order, which may increase the latency for future read operations to be performed on the blocks of data.

Aspects of the present disclosure address these and other issues through the use of a scoreboard, which is a tracking data structure to maintain operation and/or data sequentiality for media management, such as, for garbage collection. For example, when pages of valid data are read from a block during garbage collection, the scoreboard can store entries related to a sequence of read operations for garbage collection, and use these entries to maintain (e.g., track) the order in which pages are read. Accordingly, after the block has been erased, the pages of valid data can be written (e.g., re-written) to a new location in the same order in which the pages are read (e.g., in sequential order). That is, write commands for the pages of valid data can be issued to in a same order as the read commands were issued, which can result in the storage of the data to the new location in a same order as they were originally stored. By maintaining sequentiality during garbage collection, the overall performance of the memory sub-system can be improved. For example, read performance of the system may be improved, which may improve the memory sub-system's ability to aggregate read operations (e.g., into multi-plane reads). In some examples, aggregating multiple read operations can result in the memory sub-system experiencing reduced power consumption. In other cases, read speeds may be improved as data can be read at the destination location in the same order in which it was written at the source location, which may allow snap reads or other fast read operations to be performed by the memory sub-system.

Features of the disclosure are initially described in the context of a computing system as described with reference to FIG. 1. Features of the disclosure are described in the context of method diagrams and a scoreboard for maintaining sequentiality for media management for a memory sub-system as described with reference to FIGS. 2 through 4. These and other features of the disclosure are further illustrated by and described with reference to a computer system that relates to a scoreboard for maintaining sequentiality for media management as described with reference to FIG. 5.

FIG. 1 illustrates an example computing system 100 that includes a memory sub-system 110 in accordance with some embodiments of the present disclosure. The memory sub-system 110 can include media, such as one or more non-volatile memory devices (e.g., memory device 130), one or more volatile memory devices (e.g., memory device 140), or a combination thereof.

A memory sub-system 110 can be a storage device, a memory module, or a hybrid of a storage device and memory module. Examples of a storage device include a solid-state drive (SSD), a flash drive, a universal serial bus (USB) flash drive, an embedded Multi-Media Controller (eMMC) drive, a Universal Flash Storage (UFS) drive, a secure digital (SD) card, and a hard disk drive (HDD). Examples of memory modules include a dual in-line memory module (DIMM), a small outline DIMM (SO-DIMM), and a non-volatile DIMM (NVDIMM).

The computing system 100 can be a computing device such as a desktop computer, laptop computer, network server, mobile device, a vehicle (e.g., airplane, drone, train, automobile, or other conveyance), Internet of Things (IoT) enabled device, embedded computer (e.g., one included in a vehicle, industrial equipment, or a networked commercial device), or such computing device that includes memory and a processing device.

The computing system 100 can include a host system 105 that is coupled with one or more memory sub-systems 110. In some examples, the host system 105 is coupled with different types of memory sub-systems 110. FIG. 1 illustrates one example of a host system 105 coupled with one memory sub-system 110. As used herein, “coupled to” or “coupled with” generally refers to a connection between components, which can be an indirect communicative connection or direct communicative connection (e.g., without intervening components), whether wired or wireless, including connections such as electrical, optical, magnetic, etc.

The host system 105 can include a processor chipset and a software stack executed by the processor chipset. The processor chipset can include one or more cores, one or more caches, a memory controller (e.g., NVDIMM controller), and a storage protocol controller (e.g., PCIe controller, SATA controller). The host system 105 uses the memory sub-system 110, for example, to write data to the memory sub-system 110 and read data from the memory sub-system 110.

The host system 105 can be coupled to the memory sub-system 110 using a physical host interface. Examples of a physical host interface include, but are not limited to, a serial advanced technology attachment (SATA) interface, a peripheral component interconnect express (PCIe) interface, universal serial bus (USB) interface, Fiber Channel, Small Computer System Interface (SCSI), Serial Attached SCSI (SAS), a dual in-line memory module (DIMM) interface (e.g., DIMM socket interface that supports Double Data Rate (DDR)), etc. The physical host interface can be used to transmit data between the host system 105 and the memory sub-system 110. The host system 105 can further utilize a non-volatile memory Express (NVMe) interface to access the memory components (e.g., memory devices 130) when the memory sub-system 110 is coupled with the host system 105 by the PCIe interface. The physical host interface can provide an interface for passing control, address, data, and other signals between the memory sub-system 110 and the host system 105.

The memory devices can include any combination of the different types of non-volatile memory devices and/or volatile memory devices. The volatile memory devices (e.g., memory device 140) can be, but are not limited to, random access memory (RAM), such as dynamic RAM (DRAM) and synchronous DRAM (SDRAM).

Some examples of non-volatile memory devices (e.g., memory device 130) includes a NAND type flash memory. Another example of non-volatile memory device is write-in-place memory, such as three-dimensional cross-point (“3D cross-point”) memory. A cross-point array of non-volatile memory can perform bit storage based on a change of bulk resistance, in conjunction with a stackable cross-gridded data access array. Additionally, in contrast to many flash-based memories, cross-point non-volatile memory can perform a write in-place operation, where a non-volatile memory cell can be programmed without the non-volatile memory cell being previously erased.

Each of the memory devices 130 can include one or more arrays of memory cells. One type of memory cell, for example, single level cells (SLC) can store one bit per cell. Other types of memory cells, such as multi-level cells (MLCs), triple level cells (TLCs), and quad-level cells (QLCs), can store multiple bits per cell. In some embodiments, each of the memory devices 130 can include one or more arrays of memory cells such as SLCs, MLCs, TLCs, QLCs, or any combination of such. In some embodiments, a particular memory device can include an SLC portion, and an MLC portion, a TLC portion, or a QLC portion of memory cells. The memory cells of the memory devices 130 can be grouped as pages that can refer to a logical unit of the memory device used to store data. With some types of memory (e.g., NAND), pages can be grouped to form blocks.

Although non-volatile memory devices such as NAND type flash memory are described, the memory device 130 can be based on any other type of non-volatile memory, such as read-only memory (ROM), phase change memory (PCM), self-selecting memory, other chalcogenide based memories, ferroelectric RAM (FeRAM), magneto RAM (MRAM), negative-or (NOR) flash memory, electrically erasable programmable ROM (EEPROM).

The memory sub-system controller 115 (or controller 115 for simplicity) can communicate with the memory devices 130 to perform operations such as reading data, writing data, or erasing data at the memory devices 130 and other such operations. The memory sub-system controller 115 can include hardware such as one or more integrated circuits and/or discrete components, a buffer memory, or a combination thereof. The hardware can include digital circuitry with dedicated (i.e., hard-coded) logic to perform the operations described herein. The memory sub-system controller 115 can be a microcontroller, special purpose logic circuitry (e.g., a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), etc.), or other suitable processor.

The memory sub-system controller 115 can include a processor 120 (e.g., a processing device) configured to execute instructions stored in a local memory 125. In the illustrated example, the local memory 125 of the memory sub-system controller 115 includes an embedded memory configured to store instructions for performing various processes, operations, logic flows, and routines that control operation of the memory sub-system 110, including handling communications between the memory sub-system 110 and the host system 105.

In some examples, the local memory 125 can include memory registers storing memory pointers, fetched data, etc. The local memory 125 can also include read-only memory (ROM) for storing micro-code. While the example memory sub-system 110 in FIG. 1 has been illustrated as including the memory sub-system controller 115, in another example of the present disclosure, a memory sub-system 110 does not include a memory sub-system controller 115, and can instead rely upon external control (e.g., provided by an external host, or by a processor or controller separate from the memory sub-system).

In general, the memory sub-system controller 115 can receive commands or operations from the host system 105 and can convert the commands or operations into instructions or appropriate commands to achieve the desired access to the memory devices 130. The memory sub-system controller 115 can be responsible for other operations such as wear leveling operations, garbage collection operations, error detection and error-correcting code (ECC) operations, encryption operations, caching operations, and address translations between a logical address (e.g., logical block address (LBA), namespace) and a physical address (e.g., physical block address) that are associated with the memory devices 130. The memory sub-system controller 115 can further include host interface circuitry to communicate with the host system 105 via the physical host interface. The host interface circuitry can convert the commands received from the host system into command instructions to access the memory devices 130 as well as convert responses associated with the memory devices 130 into information for the host system 105.

The memory sub-system 110 can also include additional circuitry or components that are not illustrated. In some examples, the memory sub-system 110 can include a cache or buffer (e.g., DRAM) and address circuitry (e.g., a row decoder and a column decoder) that can receive an address from the memory sub-system controller 115 and decode the address to access the memory devices 130.

In some examples, the memory devices 130 include local media controllers 135 that operate in conjunction with memory sub-system controller 115 to execute operations on one or more memory cells of the memory devices 130. An external controller (e.g., memory sub-system controller 115) can externally manage the memory device 130 (e.g., perform media management operations on the memory device 130). In some embodiments, a memory device 130 is a managed memory device, which is a raw memory device combined with a local controller (e.g., local controller 135) for media management within the same memory device package. An example of a managed memory device is a managed NAND (MNAND) device.

The memory sub-system 110 includes a scoreboard manager 150 that can maintain sequentiality for media management. For example, the scoreboard manager 150 can perform operation for garbage collection, by which data is migrated from one location (e.g., a source memory address) to another location (e.g., a target or destination memory address) independent of any direct host interaction. In some examples, the scoreboard manager 150 can pack valid data together to free space for new writes, for error avoidance, for wear leveling, and/or to restore redundant array of independent nodes (RAIN) parity protection in the event of an error. Additionally or alternatively, the scoreboard manager 150 can be utilized in transferring data from one or more source blocks (e.g., one or more blocks of NAND cells) to one or more destination blocks in a same order that the data was originally written (e.g., sequentially).

In some examples, the memory sub-system controller 115 includes at least a portion of the scoreboard manager 150. For example, the memory sub-system controller 115 can include a processor 120 (e.g., a processing device) configured to execute instructions stored in local memory 125 for performing the operations described herein. In some examples, the scoreboard manager 150 is part of the host system 105, an application, or an operating system.

The scoreboard manager 150 can perform operations for media management (e.g., garbage collection) that maintain sequentiality. For example, the scoreboard manager 150 can manage (e.g., track) the pages of valid data that are read from a block during garbage collection. Specifically, the scoreboard manager 150 can track the order in which the pages are read (e.g., the order in which read commands for a given memory address at a source location are issued). After the block has been erased, which can be performed by the scoreboard manager 150 or another component, the valid data can be written (e.g., re-written) to a new location in a sequential order. That is, write commands for the valid data may be issued (e.g., by the processor 120) in a same order as the read commands were issued (i.e., in a same order as they were originally stored on the block). The write commands may be issued based on the status of one or more entries managed by the scoreboard manager 150. Further details with regards to the operations of the scoreboard manager 150 are described below.

FIG. 2 is a flow diagram of an example method 200 to maintain sequentiality for media management of a memory sub-system in accordance with some examples of the present disclosure. The method 200 can be performed by processing logic that can include hardware (e.g., processing device, circuitry, dedicated logic, programmable logic, microcode, hardware of a device, integrated circuit, etc.), software (e.g., instructions run or executed on a processing device), or a combination thereof. In some examples, the method 200 is performed by the scoreboard manager 150 of FIG. 1. Although shown in a particular sequence or order, unless otherwise specified, the order of the operations can be modified. Thus, the illustrated examples should be understood only as examples, and the illustrated operations can be performed in a different order, and some operations can be performed in parallel. Additionally, one or more operations can be omitted in various examples. Thus, not all operations are required in every example. Other method flows are possible.

At operation 205, the processing device can issue, in connection with a set of media management operations for a set of transfer units (TUs), a set of read commands according to a read sequence. In one example, the set of media management operations are for garbage collection. In other examples, the set of media management operations are for other media management algorithms, such as wear leveling, etc. A TU refers to the smallest size of data internally managed by a memory sub-system controller, local media controller, or a host system. In some examples, the set of TUs can correspond to one or more blocks of data of the memory sub-system. In some examples, the read sequence can be implicit in the set of entries. In some examples, each read command can include an instruction to read one of the TUs at a source address of a memory sub-system. In some examples, the method 200 can include receiving a set of read values for a subset of the set of TUs in response to a corresponding subset of the set of read commands. The set of read values can be received in an order different from the read sequence. In some examples, the read sequence can correspond to a physical to logical address mapping order for the set of TUs.

At operation 210, the processing device can store a set of entries associated with the set of media management operations. In some examples, each entry can include a state of the media management operations (e.g., a state of the media management operation for garbage collection) with respect to one of the TUs. In some examples, each entry can correspond to a pairing of a logical address and an associated physical address for one of the TUs.

In some examples, the method 200 can include updating the state of the media management operations for an entry of one of the TUs based at least in part on an received read value of the set of read values corresponding to the one of the TUs. In some examples, the state of the media management operations can include one of a buffer allocated state, a read request sent state, a read response received state, or a write request sent state. In some examples, the method 200 can include dropping each scoreboard entry from storage for which a corresponding invalid read response is received. In some examples, dropping a scoreboard entry can include deleting (e.g., erasing) the scoreboard entry from the scoreboard.

At operation 215, the processing device can issue a plurality write commands in connection with the set of media management operations based at least in part on the set of entries and the read sequence. In some examples, each write command can include an instruction to write one of the TUs to a respective destination address of the memory sub-system.

In some examples, the method 200 can include issuing a first read command for a first TU of the set of TUs, issuing a second read command for a second TU of the set of TUs, receiving a first read response to the first read command after receiving a second read response to the second read command, and issuing a first write command corresponding to the first read response before issuing a second write command corresponding to the second read response. In some examples, the second TU can follow the first TU in the set of entries according to the read sequence.

It should be noted that the methods described above describe possible implementations, and that the operations and the steps can be rearranged or otherwise modified and that other implementations are possible. Further, portions from two or more of the methods can be combined.

FIG. 3 illustrates an example of a method diagram 300 for maintaining sequentiality for media management of a memory sub-system in accordance with examples as disclosed herein. The method diagram 300 illustrates stages for identifying valid data (e.g., at stage 305), reading valid data (e.g., at stage 310), and issuing a write command (e.g., at stage 315). In some examples, the operations performed as described with reference to FIG. 3 can be implemented at a memory sub-system and can utilize a scoreboard 302. Further, the operations can be performed according to the operations of a host system and/or local media controller, and can be implemented based on a setting of a state machine. In some examples, the method diagram 300 can illustrate a range flow procedure 320 and a replay flow procedure 325.

The method diagram 300 can illustrate one or more media management operations for media management (e.g., media management operations for garbage collection). During garbage collection, data can be migrated (e.g., internally within a memory device) from one location (e.g., from a source memory address) to another location (e.g., to a destination memory address) independent of any direct host interaction. Garbage collection can be performed to pack valid data together, to free space for new writes, for error avoidance, for wear leveling, and/or to restore RAIN parity protection in the event of an error. Additionally or alternatively, garbage collection can consist of moving or copying data from one or more source blocks (e.g., one or more blocks of NAND cells) into one or more destination blocks. In some examples, garbage collection can result in data consolidation to free resources (e.g., NAND cells) for subsequent erase and new write processing.

In some examples, the block of data transferred during media management can be or can be referred to as a transfer unit (TU) and can be the smallest size of data internally managed by a memory sub-system controller (e.g., by the processor 120 as described with reference to FIG. 1), local media controller, or by a host system (e.g., host system 105 of FIG. 1) and corresponds to a logical address (e.g., a TU address (TUA)) and a physical address (e.g., an abstracted physical address such as a flash logical address (FLA), which may relate to a physical address of the NAND cell referred to as a platform physical address (PPA)). In order to consolidate data and/or free resources for subsequent access operations, the TU can be written to a new location (e.g., a destination address), and the original block (e.g., the block from which the TU is moved) can be erased. Candidates (e.g., a blocks) for media management (e.g., garbage collection) can be selected using a tree (a pool, a list, a queue, etc.). In some examples, the candidates can be maintained by the scoreboard 302. Based on the identification of valid TUs and the scoreboard 302 maintaining a tree, a set of sequential operations for media management (e.g., garbage collection) can be performed. As discussed herein, it can be beneficial to write TU units to a new block sequentially (e.g., in the same order that each TU is read) to improve performance of the memory sub-system.

In order to move (e.g., write) valid TUs to a destination block sequentially, the scoreboard 302 can be or can include a linked list. A linked list may be utilized by the scoreboard 302 due to its ability to maintain a sequence of entries. In other examples, the scoreboard 302 can be or can include any type of data structure that is able to maintain a sequence of entries (e.g., such as a circular buffer or a tree). Each linked list entry can include at least a TUA and an FLA associated with a TU. Additionally or alternatively, among other parameters that can be included in the linked list, the linked list can include a next node identifier. The next node identifier can indicate a subsequent TU for media management (e.g., garbage collection). Accordingly, utilizing a list where each entry indicates a next (e.g., a subsequent) TU can allow for valid TUs to be written to a destination block sequentially.

In some examples, a tree can be maintained by the scoreboard 302. A tree can consist of a list (a queue, a pool, etc.) of TUs for media management (e.g., garbage collection). For example, a read operation can occur and the TUA and/or FLA for each TU can be stored (e.g., sequentially) to the scoreboard 302 according to the order that the read commands were issued. The status of each TUA and/or FLA may be maintained in a list (e.g., a linked list) at the scoreboard 302. The order of the list (e.g., the order that read commands were issued) can allow for the TUs to be written to a destination block sequentially regardless of the order that responses to read commands (e.g., read responses) are received. In other examples, the order of the linked list can be calculated on the fly using a predictive algorithm (e.g., an algorithm to predict the order that the host system can issue read commands).

At stage 305, one or more operations can be performed to identify valid data (e.g., TUs). Although a count of valid TUs in a block can be readily available (e.g., available to a controller), a location of each valid TU can be identified. In some examples, a location of valid TUs can be identified using a range flow procedure 320 or a replay flow procedure 325. A range flow procedure 320 can include processing commands that fold data (e.g., move data and organize data) of an entire memory sub-system. Additionally or alternatively, a replay flow procedure 325 can use a buffer (e.g., read buffer 335) and can cycle through physical locations in a block.

At stage 310, one or more operations can be performed to read valid data (e.g., TUs) that was identified at stage 305. For example, after valid TUs are identified, an FLA corresponding to each valid TU can be compared with the tree maintained by the scoreboard 302. If the FLA corresponding to a valid TU matches an FLA maintained by the scoreboard 302, then a read command associated with the valid TU can occur. Conversely, if the FLAs do not match, the entry maintained by the scoreboard 302 can be released (e.g., moved to the end of the linked list). In other examples, if the FLAs do not match, the system can be configured to continue cycling through valid TUs until an FLA matches the entry maintained by the scoreboard 302.

At stage 315, one or more operations can be performed to write valid data (e.g., TUs) that were read at stage 310. As discussed herein, when an FLA corresponding to a valid TU matches an FLA maintained by the scoreboard 102, a read command associated with the valid TU is issued. Additionally or alternatively, based on the read command being issued, data associated with the valid TU can be written (e.g., moved) into a destination block (e.g., to a destination address). Due to the use of a linked list, data associated with valid TUs can be written to a destination block sequentially.

At stage 305, various methods can be employed to determine valid data (e.g., valid TUs). For example, a replay flow procedure 325 can support the determination of valid data by iterating through various TUs stored within a buffer (e.g., within a read buffer 335). The buffer can include one or more addresses (e.g., TUAs and/or FLAs) that correspond to locations in a block from which a respective TU was read. In some examples, a replay flow procedure 325 can be selected based on one or more settings associated with a mode register and/or a controller (e.g., memory sub-system controller, a local media controller). In some examples, a replay flow procedure 325 can be performed in multiple stages (e.g., a first stage 330 and a second stage 340).

When the replay flow procedure 325 is employed, a signal 371 can be received by the read buffer 335 during the first stage 330. The signal 371 can initiate the read buffer 335 to cycle through one or more TUs (e.g., as illustrated by 373)). That is, the read buffer 335 can map (e.g., determine, identify, etc.) a TUA and an FLA of a potentially valid TU according to an order in which read commands are issued. During the second stage 340, the TUA and FLA of each TU can be identified and provided to the scoreboard 302 (e.g., via signal 375 and/or signal 369). In some examples, the first stage 330 and the second stage 340 can be asynchronous (e.g., a duration can occur between the onset of the first stage 330 and the completion of the second stage 340).

After identifying and providing the TUA and the FLA to the scoreboard the list (e.g., the linked list) can be compiled at the scoreboard 302. In some examples, a lookup of the TUA and FLA can then be issued (e.g., at 350) to determine whether the associated data remains valid, and if so, the valid data can be written to a destination block (e.g., sequentially). In some examples, the lookup 350 can occur in an order that read responses are received, and can be performed to determine whether the TUA and FLA match an entry of the tree stored at the scoreboard 302. Because the tree can utilize a linked list, the TUAs and FLAs stored to the scoreboard 302 can be compared to a respective TUA and FLA of each received read response (e.g., compared in order). Depending on the results of the comparison, a read command can be issued and the TU can be written to a destination block.

A range flow procedure 320 can include processing commands that fold data (e.g., move data and organize data) of an entire memory sub-system. For example, a range flow procedure 320 can be selected based on one or more settings associated with a mode register and/or a controller (e.g., memory sub-system controller, a local media controller). That is, using a range flow procedure 320 can be optional. In some examples, a range flow procedure 320 can include a request being made to indicate a start and end listing of TUAs to be scanned. In some examples, when such a request is made (i.e., identified by a memory sub-system controller and/or a host system), a flag is set to direct firmware along the listing of TUAs to be scanned.

When a range flow procedure 320 is employed, a read command for each FLA in a particular block can be issued. A corresponding TUA and FLA can be stored to the scoreboard 302 as part of a list (e.g., a linked list). In some examples, a lookup of the TUA and FLA can then be issued (e.g., at 350) to determine whether the associated data remains valid, and to write (e.g., sequentially) the valid data to a destination block. Because the tree can utilize a linked list, the TUA and FLA identified can be compared with a first entry of the list (e.g., the head of the list). Depending on the results of the comparison, a read command can be issued and the TU can be written to a destination block.

In some examples, both a range flow procedure 320 and a replay flow procedure 325 can result in a lookup 350 being performed to determine whether a read response (e.g., a TUA and FLA corresponding to a read response) matches an entry of the tree stored at the scoreboard 302. Accordingly, the TUA and FLA associated with the read response can be provided to the scoreboard 302 via signal 381. The signal 381 can be transmitted to the scoreboard 302 by a controller or other component. In some examples, the signal 381 can be transmitted to the scoreboard 302 at a first time (e.g., at 350; not shown) and a result of the comparison can be received at a second time (e.g., at 355 via signal 383). Accordingly, in some examples, a portion of the comparison can occur at (e.g., during) the stage 305 and at (e.g., during) the stage 310. In some examples, steps performed at 350 and at 355 can be asynchronous (e.g., a duration can occur between steps performed by various components at 350 and 355).

As read responses are received, a corresponding TUA and FLA can be compared with a first entry (e.g., the head of the list) of the tree stored at the scoreboard 302. In some instances, the TUA and FLA may not match the first entry. For example, the comparison of the first entry with the first received TUA and FLA can indicate that the entries do not match. In such an example, the first entry of the list can be released (e.g., moved to the bottom of the list). Accordingly, the TUA and FLA can be compared with a subsequent entry (or entries) in the list until a match is determined. Once a match is determined, a read of the associated TU can be issued (e.g., at 360), and the TU can be subsequently written to a destination block (e.g., at 365, which can occur at the stage 315). In some examples, the stage 310 and the stage 315 can be asynchronous (e.g., a duration can occur between the two stages).

A TUA and FLA associated with each valid TU can be compared with the list in the manner described herein. When a match does not exist, the entry in the scoreboard can be released. Conversely, when a match exists, a read can be issued and the TU can be written to the destination block. When a TU is written to the destination block (e.g., when a write command is issued at 365) the associated entry in the scoreboard 302 can be released. Accordingly, such a process can result in TUs being written to a destination block in a same order as a read commands were issued, which can maintain sequentiality throughout media management (e.g., garbage collection).

FIG. 4 illustrates an example block diagram 400 of media management operations for maintaining sequentiality for garbage collection in accordance with examples as disclosed herein. The operations illustrate a read sequence 405, read responses 410, and write commands 415. In some examples, the write commands 415 can be based on the order of the read sequence 405 and the read responses 410 during garbage collection. Additionally or alternatively, the operations can be implemented using a scoreboard 425, which can be an example of a scoreboard 302 as described with reference to FIG. 3. In some examples, the scoreboard 425 can include one or more scoreboard entries 420 that facilitate garbage collection, such as entries of a tree as described with reference to FIG. 3.

In some examples, FIG. 4 illustrates operations of garbage collection. As discussed herein, garbage collection can occur to migrate data from one location to another location independent of any direct host system interaction. In the context of FIG. 4, each of the read sequence 405, the read responses 410, and the write commands 415 can be associated with a block (e.g., a block of data). Each block can include one or more pages capable of storing a finite amount of data. For example, each block can include 32 pages that are each capable of storing 4 kilobytes (KB) or 8 KB of data (or other amount). For illustrative purposes, each of the read sequence 405, the read responses 410, and the write commands 415 illustrate twelve (12) blocks of valid data (numbered 1 through 12) and various blocks of dirty/stale data and/or erased data. Dirty data is the latest version of data in cache memory that had not been saved to media (e.g., NAND). Stale data includes data that was previously written but is no longer associated with a valid logical address, such as a logical address referenced by a host system in a physical to logical (P2L) mapping table. Each block of valid data (e.g., 1 through 12) can be or can be referred to as a TU.

A range flow procedure (e.g., range flow procedure 320 as described with reference to FIG. 3) and/or a replay flow procedure (e.g., replay flow procedure 325 as described with reference to FIG. 3) can be associated with a read sequence 405. For example, a range flow procedure and/or a replay flow procedure can issue one or more read commands for reading TUs for garbage collection. As shown in FIG. 4, and for illustrative purposes only, a read sequence 405 can issue one or more read commands for TUs 1 through 12. The read sequence 405 can issue the read commands simultaneously, such that a read command for each subsequent TU is issued in order (i.e., a read command for each TU is issued consecutively). The read commands can be stored to the scoreboard 425 as a list (e.g., a linked list, a circular buffer, or a tree). In some examples, a TUA and FLA associated with each TU can be stored as a scoreboard entry 420 in a scoreboard 425 (e.g., scoreboard 302 of FIG. 3) maintained by a scoreboard manager (e.g., scoreboard manager 150 of FIG. 1).

In some examples, the scoreboard entries 420 can store a respective value associated with each TU. That is, the scoreboard 425 and the scoreboard entries 420 can act as a buffer that maintains read values for each TU of garbage collection. Accordingly, when an associated read response is received (i.e., a response associated with a TUA and FLA stored to the scoreboard 425), the respective value can be updated. A listing of some potential states reflected by a scoreboard entry is illustrated below in Table 1. The states reflected in Table 1 may reflect a scoreboard entry at any one point in time.

TABLE 1 Value Meaning 0 Empty 1 Found TUA/FLA pair 2 Lookup request sent 3 Lookup response received 4 Buffer allocated 5 Read request sent 6 Read response received 7 Write request sent

As shown in Table 1, the scoreboard 425 can include a variety of entries. Each of the pages (and TUs 1 through 12) may be associated with a respective entry. For example, some pages (and TUs) may be associated with a same entry, and other pages (and TUs) may be associated with a different entry. Each entry represents a current state of a respective page and/or TU.

In some examples, entry “0” represents an empty state. An empty state may indicate that the page is empty (e.g., it has been previously erased) and no valid data is to be read from the page and/or that the page is free to be written to. In some examples, entry “1” represents that a TUA and FLA have been identified. In some examples, entry “2” represents that a lookup has been performed on the TUA and FLA to determine if the associated data is still valid.

In some examples, entry “3” represents that a response regarding whether the data associated with the TUA and FLA is valid. If the data is valid, the entry remains on the scoreboard. If the data is invalid, the entry may be moved to the end of the linked list and assigned a “0”. In some examples, entry “4” represents the valid data being allocated to the buffer (e.g., the read buffer 335 with reference to FIG. 3). In some examples, entry “5” represents that the valid data associated with the TUA and FLA has been read.

In some examples, entry “6” represents that the valid data associated with the TUA and FLA has been received. In some examples, entry “7” represents that the valid read data is to be written. After the data has been written, the entry may be assigned a “0” and may be moved to the end of the linked list. This may indicate that the data was successfully (and sequentially) written back.

After issuing a read sequence 405, read responses 410 can be received (e.g., at the scoreboard 425) in a non-sequential order. For example, as shown in FIG. 4, each response can be received in a non-sequential order or at least in a different order than the read sequence 405 was issued. Receiving the read responses 410 in a non-sequential order can be due to a variety of reasons, including but not limited to, particular channels being temporarily utilized for different operations (e.g., for host read operations). If the read responses 410 are written to a destination block in the received order (i.e., the non-sequential order), an overall performance of the memory sub-system can be reduced. Accordingly, it can be beneficial to issue write commands 415 in a sequential order as shown in FIG. 4.

In order to issue the write commands 415 in a same order as the read sequence 405 was issued, a list (e.g., a linked list) can be maintained by the scoreboard 425. As discussed herein, as read responses 410 are received, a corresponding TUA and FLA can be compared with a first entry (e.g., the head of the list) of the list stored at the scoreboard 425. For example, when read response “1” (i.e., the first valid TU) is received, it can be compared with the first entry of the read sequence 405 that is stored at the scoreboard 425. Because the entries (e.g., an associated TUA and FLA of the entries) match, the read response “1” can be first-written to the destination block. That is, a write command 415 associated with the read response “1” can be first-issued. In the case that the read response “1” was not first-received—for example, if a read response “2” was first received—the entries would not match. Accordingly, the entry associated with the TU “1” stored at the scoreboard 425 can be released (e.g., moved to the bottom of the list). The read response “2” can then be compared with the next stored entry—the TU “2” stored at the scoreboard. Because these entries match, the read response “2” can be first-written to the destination block. This process can continue such that the TUs are written (e.g., write commands are issued) to a destination block in a sequential order (e.g., in the order in which read commands were issued). By writing each TU to a destination block in a sequential order, performance of the associated memory sub-system can be improved.

FIG. 5 illustrates an example machine of a computer system 500 that supports a maintaining sequentiality for media management in accordance with examples as disclosed herein. The computer system 500 can include a set of instructions, for causing the machine to perform any one or more of the techniques described herein. In some examples, the computer system 500 can correspond to a host system (e.g., the host system 105 described with reference to FIG. 1) that includes, is coupled with, or utilizes a memory sub-system (e.g., the memory sub-system 110 described with reference to FIG. 1) or can be used to perform the operations of a controller (e.g., to execute an operating system to perform operations corresponding to the scoreboard manager 150 described with reference to FIG. 1). In some examples, the machine can be connected (e.g., networked) with other machines in a local area network (LAN), an intranet, an extranet, and/or the Internet. The machine can operate in the capacity of a server or a client machine in client-server network environment, as a peer machine in a peer-to-peer (or distributed) network environment, or as a server or a client machine in a cloud computing infrastructure or environment.

The machine can be a personal computer (PC), a tablet PC, a set-top box (STB), a Personal Digital Assistant (PDA), a cellular telephone, a web appliance, a server, a network router, a switch or bridge, or any machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that machine. Further, while a single machine is illustrated, the term “machine” can also include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein.

The example computer system 500 can include a processing device 505, a main memory 510 (e.g., ROM, flash memory, DRAM such as SDRAM or Rambus DRAM (RDRAM), etc.), a static memory 515 (e.g., flash memory, static RAM (SRAM), etc.), and a data storage system 525, which communicate with each other via a bus 545.

Processing device 505 represents one or more general-purpose processing devices such as a microprocessor, a central processing unit, or the like. More particularly, the processing device can be a complex instruction set computing (CISC) microprocessor, reduced instruction set computing (RISC) microprocessor, very long instruction word (VLIW) microprocessor, or a processor implementing other instruction sets, or processors implementing a combination of instruction sets. Processing device 505 can also be one or more special-purpose processing devices such as an ASIC, an FPGA, a DSP, network processor, or the like. The processing device 505 is configured to execute instructions 535 for performing the operations and steps discussed herein. The computer system 500 can further include a network interface device 520 to communicate over the network 540.

The data storage system 525 can include a machine-readable storage medium 530 (also known as a computer-readable medium) on which is stored one or more sets of instructions 535 or software embodying any one or more of the methodologies or functions described herein. The instructions 535 can also reside, completely or at least partially, within the main memory 510 and/or within the processing device 505 during execution thereof by the computer system 500, the main memory 510 and the processing device 505 also constituting machine-readable storage media. The machine-readable storage medium 530, data storage system 525, and/or main memory 510 can correspond to a memory sub-system.

In one example, the instructions 535 include instructions to implement functionality corresponding to a scoreboard manager 550 (e.g., the scoreboard manager 150 described with reference to FIG. 1). While the machine-readable storage medium 530 is shown as a single medium, the term “machine-readable storage medium” can include a single medium or multiple media that store the one or more sets of instructions. The term “machine-readable storage medium” can also include any medium that is capable of storing or encoding a set of instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies of the present disclosure. The term “machine-readable storage medium” can include, but not be limited to, solid-state memories, optical media, and magnetic media.

Some portions of the preceding detailed descriptions have been presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the ways used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of operations leading to a desired result. The operations are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. The present disclosure can refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage systems.

The present disclosure also relates to an apparatus for performing the operations herein. This apparatus can be specially constructed for the intended purposes, or it can include a general purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program can be stored in a computer readable storage medium, such as, but not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions, each coupled to a computer system bus.

The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general purpose systems can be used with programs in accordance with the teachings herein, or it can prove convenient to construct a more specialized apparatus to perform the method. The structure for a variety of these systems will appear as set forth in the description below. In addition, the present disclosure is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages can be used to implement the teachings of the disclosure as described herein.

The present disclosure can be provided as a computer program product, or software, that can include a machine-readable medium having stored thereon instructions, which can be used to program a computer system (or other electronic devices) to perform a process according to the present disclosure. A machine-readable medium includes any mechanism for storing information in a form readable by a machine (e.g., a computer). In some examples, a machine-readable (e.g., computer-readable) medium includes a machine (e.g., a computer) readable storage medium such as a ROM, RAM, magnetic disk storage media, optical storage media, flash memory components, etc.

In the foregoing specification, examples of the disclosure have been described with reference to specific example examples thereof. It will be evident that various modifications can be made thereto without departing from the broader spirit and scope of examples of the disclosure as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense. 

What is claimed is:
 1. A method comprising: issuing, in connection with a set of media management operations for a plurality of transfer units, a plurality of read commands according to a read sequence, each read command comprising an instruction to read one of the transfer units at a source address of a memory sub-system; storing a plurality of entries associated with the set of media management operations, each entry comprising a state of the set of media management operations with respect to one of the transfer units, wherein the read sequence is implicit in the plurality of entries; receiving a first subset of read responses according to a read response sequence, wherein the first subset of read responses is associated with a second subset of the plurality of read commands, and wherein the read response sequence is different than the read sequence; and issuing a write command for each received read response of the first subset of read responses, wherein each write command is issued according to the read sequence and comprises an instruction to write one of the transfer units to a respective destination address of the memory sub-system.
 2. The method of claim 1, further comprising: receiving a set of read values for a third subset of the plurality of transfer units in response to a corresponding fourth subset of the plurality of read commands, wherein the set of read values are received in an order different from the read sequence.
 3. The method of claim 2, further comprising: updating the state of the set of media management operations for an entry of one of the transfer units based at least in part on a received read value of the set of read values corresponding to the one of the transfer units.
 4. The method of claim 1, wherein each entry corresponds to a pairing of a logical address and an associated physical address for one of the transfer units.
 5. The method of claim 1, further comprising: issuing a first read command for a first transfer unit of the plurality of transfer units; issuing a second read command for a second transfer unit of the plurality of transfer units, wherein the second transfer unit follows the first transfer unit in the plurality of entries according to the read sequence; receiving a first read response to the first read command after receiving a second read response to the second read command; and issuing a first write command corresponding to the first read response before issuing a second write command corresponding to the second read response.
 6. The method of claim 1, further comprising: dropping each scoreboard entry from storage for which a corresponding invalid read response is received.
 7. The method of claim 1, wherein the state of the set of media management operations comprises one of a buffer allocated state, a read request sent state, a read response received state, or a write request sent state.
 8. The method of claim 1, wherein the plurality of transfer units corresponds to one or more blocks of data of the memory sub-system.
 9. The method of claim 1, wherein the read sequence corresponds to a physical to logical address mapping order for the plurality of transfer units.
 10. A system comprising: a plurality of memory devices; and a processing device, operatively coupled with the plurality of memory devices, to: issue, in connection with a set of media management operations for a plurality of transfer units, a plurality of read commands according to a read sequence, each read command comprising an instruction to read one of the transfer units at a source address of a memory sub-system; store a plurality of entries associated with the set of media management operations, each entry comprising a state of the set of media management operations with respect to one of the transfer units, wherein the read sequence is implicit in the plurality of entries; receive a first subset of read responses according to a read response sequence, wherein the first subset of read responses is associated with a second subset of the plurality of read commands, and wherein the read response sequence is different than the read sequence; and issue a write command for each received read response of the first subset of read responses, wherein each write command is issued according to the read sequence and comprises an instruction to write one of the transfer units to a respective destination address of the memory sub-system.
 11. The system of claim 10, further comprising: the processing device further to: issue a plurality of read commands according to the read sequence in connection with the set of media management operations for the plurality of memory devices; and update the state for an entry corresponding to a memory device for which a response to an associated read command is received.
 12. The system of claim 10, further comprising: the processing device further to: issue a plurality of write commands according to the read sequence, each write command comprising an instruction to write data of one of the memory devices to a respective destination address of the memory sub-system.
 13. A non-transitory computer-readable storage medium comprising instructions that, when executed by a processing device, cause the processing device to: issue, in connection with a set of media management operations for a plurality of transfer units, a plurality of read commands according to a read sequence, each read command comprising an instruction to read one of the transfer units at a source address of a memory sub-system; store a plurality of entries associated with the set of media management operations, each entry comprising a state of the set of media management operations with respect to one of the transfer units, wherein the read sequence is implicit in the plurality of entries; receive a first subset of read responses according to a read response sequence, wherein the first subset of read responses is associated with a second subset of the plurality of read commands, and wherein the read response sequence is different than the read sequence; and issue a write command for each received read response of the first subset of read responses, wherein each write command is issued according to the read sequence and comprises an instruction to write one of the transfer units to a respective destination address of the memory sub-system.
 14. The non-transitory computer-readable storage medium of claim 13, wherein the processing device is further to: receive a set of read values for a third subset of the plurality of transfer units in response to a corresponding fourth subset of the plurality of read commands, wherein the set of read values are received in an order different from the read sequence.
 15. The non-transitory computer-readable storage medium of claim 14, wherein the processing device is further to: update the state of the set of media management operations for an entry of one of the transfer units based at least in part on an received read value of the set of read values corresponding to the one of the transfer units.
 16. The non-transitory computer-readable storage medium of claim 13, wherein each entry corresponds to a pairing of a logical address and an associated physical address for one of the transfer units.
 17. The non-transitory computer-readable storage medium of claim 13, wherein the processing device is further to: issue a first read command for a first transfer unit of the plurality of transfer units; issue a second read command for a second transfer unit of the plurality of transfer units, wherein the second transfer unit follows the first transfer unit in the plurality of entries according to the read sequence; receive a first read response to the first read command after receiving a second read response to the second read command; and issue a first write command corresponding to the first read response before issuing a second write command corresponding to the second read response.
 18. The non-transitory computer-readable storage medium of claim 13, wherein the processing device is further to: drop each entry from storage for which a corresponding invalid read response is received.
 19. The non-transitory computer-readable storage medium of claim 13, wherein the state of the set of media management operations comprises one of a buffer allocated state, a read request sent state, a read response received state, or a write request sent state.
 20. The non-transitory computer-readable storage medium of claim 13, wherein the plurality of transfer units corresponds to one or more blocks of data of the memory sub-system. 